Explosive-forming device

ABSTRACT

An explosive-forming device has walls surrounding a pressure chamber arranged to accommodate a workpiece and a die whose surface contour is to be imparted to the workpiece for shockdeformation of the latter into conformance with the surface contour. A recess is provided in the wall means and has an opening communicating with the pressure chamber. A gunpowder charge is accommodated in the recess and fills the same partly. Damping means is arranged in the remainder of the recess intermediate the charge and the opening of the recess and fills at least a part of this remainder of the recess.

United States Patent liiiertel et al.

[54] lEXlPLQSii/lE-WURMIENG DEJINJIE [72] Inventors: Heinrich ll'llertel, Tannenbergallee 36, 1

Berlin 19; Dietrich llinppin, Berlin, both of Germany [73] Assignee: said lillertel, [by said Ruppin [22] Filed: Sept. 241, 11969 [21] App]. No; 860,703

[30] Foreign Application Priority Data Sept. 25, 1968 Germany ..P 17 77 207.5

[52] US. U1. ..72/56 [51] lint. Cl ..BZM 26/00 [58] Field of Search ...72/56; 29/421 E [56] References Cited UNITED STATES PATENTS 2,935,038 5/1960 Chatten ..72/56 3,036,373 5/ 1962 Drexelius. .....72/56 3,045,339 7/1962 Callahan ..72/56 [151 Addlifidil [451 who 22, 1972 3,127,923 4/1964 Cadwell ..72/56 3,195,334 7/1965 Filler ..72/56 OTHER PUBLICATIONS Explosives From Space Age Shapes" pp. 82 86, Aug. 25, 1958; Steel.

Primary Examiner-Richard J. l-llerbst Att0mey-Michael S. Striker [57] ABSTRACT An explosive-forming device has walls surrounding a pressure chamber arranged to accommodate a workpiece and a die whose surface contour is to be imparted to the workpiece for shock-deformation of the latter into conformance with the surface contour. A recess is provided in the wall means and has an opening communicating with the pressure chamber. A gunpowder charge is accommodated in the recess and fills the same partly. Damping means is arranged in the remainder of the recess intermediate the charge and the opening of the recess and fills at least a part of this remainder of the recess.

110 Claims, 5 Urawing Figures PAIENMrzazz I972 SHEET 1 OF 2 INVENTORE: EW 62 06M H BY P:

BACKGROUND OF THE llNVENTllON The present invention relates generally to devices for shock deformation of workpieces, and more particularly to such devices which have a self-venting pressure chamber, and still more particularly to such devices which use explosive charges for producing the shock pressure necessary to obtain the workpiece deformation.

The forming or deformation of workpieces by shock, that is by setting off explosives or analogous means, is already known. It is also known to utilize self-venting pressure chambers in such devices, that is pressure chambers wherein one or more walls move to a position in which the pressure chamber is opened when the pressure in the chamber reaches and exceeds a predetermined level. The means for maintaining the movable wall or walls in closed position against the developing pressure--until the pressure reaches the predetermined level-usually require significant structural and technological expenditures because of the forces which must be restrained. German Pat. No. 1,259,825 teaches an attempt to simplify such devices wherein the pressure chamber is bounded by stationary and movable walls, with the mass of the movable walls being so selected that the developing pressure in the interior of the pressure chamber is largely counteracteduntil it reaches the predetermined level at which venting is desiredby the inertia of the masses involved. This is a significant improvement over the constructions known prior to this teaching because it makes possible the construction of devices of the type under discussion which are much simpler and therefore less expensive than heretofore possible, and which can be smaller and therefore more readily accommodated even where space is at a premium.

lf shock-pressure deformation devices utilize gunpowder to obtain the necessary pressure buildup, for instance in form of gunpowder cartridges, then the requirements made of the charge are considerably different from those which are for instance made of gunpowder used in ammunition for weapons. This is especially important in devices of the type described in the aforementioned German Pat. No. 1,259,825 where it is essential for proper operation of the concept of maintaining the pressure chamber closed for the requisite deformation time by the inertia of the masses involved, that the pressure which develops upon combustion of the charge rise in as brief as possible a time to as high as possible a pressure peak. Such pressure peaks are not desired in ammunition for weapons because of the high-and for weaponry purposes unnecessary-stresses which they impose upon the barrel of the weapon.

A further consideration in the type of device here specifically under discussion is the fact that the explosive charge is arranged adjacent the preferably liquid pressure-transmitting medium accommodated in the interior of the pressure chamber. This makes it difficult to obtain a complete combustion of the charge because under certain circumstances the pressure-transmitting liquid may prevent the combustion of a portion of the charge. This is another problem which is not encountered in ammunition for projectile weapons because in such applications the entire time period during which the projectile traverses the length of the weapons barrel is available for the combustion of the gunpowder charge.

The obvious answer to these problems in conjunction with the explosive-forming devices under discussion would appear to be to use specially formulated gunpowder, it being well known that the pressure development time subsequent to ignition of the charge can be influenced by the size of the gunpowder grain as well as by the conformation of the individual grains. The necessary steep pressure rise can be readily obtained by using gunpowder of sufficiently fine grain and having degressive combustion characteristics, that is gunpowder whose grain is ball-shaped in configuration.

However, this apparent solution is illusory because it has been found that the use of gunpowder of this type subjects the chamber accommodating the charge-particularly if the charge involves quantities of gunpowder in excess of IO grams-to stresses which are higher than is acceptable. Specifically, these stresses exceed 110,000 atmospheres. Furthermore, it has been found that even if this were no consideration the use of such specially formulated gunpowder would still not entirely avoid the problems in question because even this special gunpowder will not be completely combusted under the circumstances outlined above with reference to the explosive-forming devices in question. Of course, insufficient combustion brings with it two distinct problems, namely on the one hand deformation results which vary from case to case and on the other hand, a safety risk because the noncombusted portion of the charge may become deposited somewhere in or on the device and will become combustible again after drying.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to provide an improved device for shock-deformation of workpieces.

A more specific object of the invention is to provide such a device which, when used with a gunpowder charge as the shock-pressure producing means is not possessed of the aforementioned disadvantages.

ln pursuance of the above objects, and others which will become apparent hereafter, one feature of the invention resides in an explosive-forming device which, briefly stated, comprises wall means surrounding a pressure chamber arranged to accommodate a workpiece and a die having a surface contour which is to be imparted to said workpiece for shock-deformation of the latter into conformance with the surface contour. The wall means includes at least two walls at least one of which is movable relative to the other between a chamber-closing chamber and a chamber-opening position and the wall means has an inertia so selected as to at least substantially equal the necessary shock-pressure for producing the predetermined energy level requisite to obtain the desired deformation of the workpiece so that upon exceeding of this shock pressure relative movement of the walls to chamberopening position results with concomitant venting of the chamber.

In accordance with the invention the shock-pressure producing means which is provided for producing a sudden increase in pressure in this chamber, includes a recess provided in the wall means and having an opening which communicates with the pressure chamber, and a gunpowder charge accommodated in this recess partly filling the same. Furthermore, the shock-pressure producing means includes damping means accommodated in the remainder of the recess intermediate the charge and the opening and filling at least a portion of this remainder.

The remainder which is not filled by the gunpowder charge constitutes, of course, an expansion chamber. 0n ignition and combustion of the charge the damping means is of course driven towards the opening of the recess so that intermediate the damping means and the combusting charged there develops the necessary space required for proper combustion. Because in accordance with the invention at least the portion of the recess which does not accommodate the charge is of substantially tubular configuration in its interior, the damping means is prevented from scattering under the stresses trans mitted to it by the igniting charge and thus serves to fulfill its separating function-separating the gunpowder charge from the pressure-transmitting liquid in the interior of the pressure chamber-for the period of time during which it moves to and out of the opening and into the pressure chamber. Of course, when it enters the pressure chamber it scatters but by this time the charge is already completely combusted. Furthermore, the presence of the damping means makes it possible to use coarser gunpowder and to thereby reduce the stresses on the wall means accommodating the charge.

The effectiveness of the device according to the present invention is largely independent of the type of material used for the damping means. It is therefore possible to use for this purpose materials which decompose into small particles upon entering into the pressure chamber, such as felt, paper board, nonvulcanized rubber and similar materials, and which therefore do not pose any threat of damage to the workpiece, the die or any other components contained in the pressure chamber, or to the walls of the pressure chamber.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 3 is a view similar to FlG. 2 but illustrating an additional embodiment of the invention;

FIG. 4 is a view similar to H6. 2 but illustrating still a further embodiment of the invention; and

FIG. 5 is also a view similar to FlG. 2 but illustrating yet another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing firstly FIG. 1 it is reiterated that this is a somewhat diagrammatic cross section through an apparatus embodying the present invention. All such components which have not been considered necessary for an understanding of the present invention have been omitted to avoid confusion.

Keeping this in mind it is pointed out that reference numeral 4 identifies an upper mass and reference numeral 5 a lower mass which are connected for movement relative to one another by the diagrammatically illustrated guide rods 7. Relative movement of the masses 4 and 5 thus occurs in direction axially of these guide rods 7.

Of course, it will be appreciated that the masses d and 5 constitute wall means and that their mass is so selected that when they are in the position illustrated in Fit]. 1 in which they define with one another an interior pressure chamber which is shown as being filled with a liquid pressure-transmitting medium 8, they will be capable of resisting the tendency of the internal pressure which develops and rises upon ignition of an explosive charge to move them apart, until such time as the pressure has reached the level necessary to deform the workpiece 110 which is shown as overlying a mold 9 accommodated in the interior of the pressure chamber and provided in this embodiment with a recessed surface contour into conformance with which the workpiece i0 is to be deformed. In conventional manner the space 13 defined between the surface of the mold 9 and the underside of the workpiece it) may be evacuated by the evacuating conduit 12 which of course is connected to a suitable source of underpressure.

No separate means are needed for maintaining this pressure chamber closed until the deformation pressure in it is reached, because of the selection of the masses of the elements 4 and S in such a manner that the inertia of these masses resists the shock-pressure until the latter has reached the aforementioned predetermined level. It will be appreciated, of course, that this is the reason why the increase in the pressure must be extremely rapid so that the deformation level can be reached before the inertia of the masses is overcome so that they begin to move apart and venting of the interior of the chamber can occur. Evidently, should this occur prematurely the deformation of the work piece would either not take place or would be inadequate.

it is thought to be self-evident that the mass 5 will be supported in suitable manner, for instance by springs or the like which are not, however, illustrated because they form no part of the invention and are not essential for an understanding of the invention. In fact, what has been described heretofore is known from the art. I

in accordance with the invention, however, a recess is provided-in FIG. 1 in the mass 4-which accommodates an explosive gunpowder charge ll, for instance a cartridge of well known construction, an ignition device 6 for igniting the gunpowder charge and which may also be of any suitable construction and forms no part of the invention, and damping means 2. in the embodiment of F [G l the charge 1 fills a part of this recess, and the damping means 2 fills a portion of the remainder of the recess. An unfilled portion 3 of the recess constitutes an expansion space which is shown as having a cross-sectional area smaller than the smallest cross-sectional area of the part of the recess which accommodates the charge 1 and the damping means 2. Of course, it is evident from FIG. 11 that the interior of the recess is accessible from the exterior of the mass 4 and pressure chamber, to permit introduction of the damping means 2, the cartridge l and the ignition device 6. How the open end of the recess at the exterior of the mass 4 is closed to prevent ejection through this open end, forms no part of the invention as will be readily understandable to those skilled in the art.

Having the portion 3 of the recess provided with a smaller cross-sectional area than the other portions thereof, has on the one hand the advantage that the insertion of the damping means 2 is facilitated because it will be held in place and prevented from falling through into the interior of the pressure chamber. 0n the other hand, this reduction in cross-sectional area facilitates the effectiveness of the damping means 2 because upon ignition of the charge l the damping means 2 is forced at increased friction through the portion 3 and its damping effectiveness is therefore improved.

On exit of the damping means 2 from the opening with which the portion 3 of the recess communicates with the interior of the pressure chamber, the shock pressure necessary to obtain the deformation of the workpiece it) rapidly develops in the pressure chamber and is contained therein against ventinguntil it reaches the aforementioned predetermined value at which it has performed at the desired deformation of the workpieceby the inertia of the masses 4 and 5.

The configuration of the portion 3, in conjunction with mass forces and frictional forces involved, prevents the material of the damping means 2 from decomposing or disintegrating while it is still in the recess portion 3. Instead, the damping means 2 is forced as a solid plug outwardly through the opening with which the portion 3 communicates with the interior of the pressure chamber. This is true even if the material of the damping means 2 has low mechanical strength, such as felt, paper board, uncured rubber or the like. During the movement of the damping means 2 through the portion 3 of the recess the presence of the damping means in form of a solid plug prevents the ejection of as yet uncombusted grains of gunpowder into the pressure-transmitting liquid 8 and thus assures complete combustion of the charge ll. At the same time the period of time required for the damping means 2 to reach and pass through the opening of the portion 3 which communicates with the interior of the chamber containing the pressure liquid 8, is available for development of the combustion pressure to peak value. This makes it possible to use relatively coarse-grained gunpowder with correspondingly longer combustion time. It will thus be appreciated that the steep pressure increase in the pressure-transmitting liquid 8which is necessary for proper operation of the device-will be obtained regardless of the manner in which pressure buildup occurs in the portion 3-which constitutes an expansion chamber-on exit of the damping means 2 from the portion 3.

As FIG. 2 shows, the configuration of the recess may be different from that illustrated in FIG. i. in FIG. 2 the portion 3 corresponding to the portion 3 of FIG. 1 tapers conically towards the opening communicating with the interior of the pressure chamber and therefore with the pressure-transmitting liquid 8. Reference numeral it again identifies the charge and reference numeral 2'. the damping means. It will be seen that ignition of the charge l drives the damping means 2 towards the opening of the portion 3' which communicates with the interior of the pressure chamber. During such movement of the damping means 7. the latter will be continuously compressed, that is it will continuously have its diameter reduced. This results in a constant increase of the friction between the damping means and the inner circumferential surface bounding the portion 3, and facilitates disintegration of the damping means 3 upon ejection of the latter into the interior of the pressure chamber. As already pointed out, such disintegration is desirable to avoid damage to the interior of the pressure chamber and to all components including the workpiece accommodated therein.

A further embodiment for possible configuration of the recess is illustrated in EEG. 3. in this Figure the recess is of cylindrical configuration and of constant cross section throughout. its cross section corresponds to that of the explosive charge l, which in all of HUS. 2-5 is illustrated as accommodated in a cartridge. Evidently, from a point of view of manufacture the embodiment in FlG. 3 is simplest, because a cylindrical recess of constant cross section is easiest to produce. However, it does require that the material and geometry of the plug of damping material 2 be so selected that it will move through the portion 3 of the recess with the friction requisite for obtaining the desired results which have been outlined earlier.

The embodiment illustrated in HQ. t corresponds basically to that shown in FIG. ll, except that in hit}. at the plug of damping material 2' is not accommodated freely in the recess but instead in the interior of the cartridge 1', with reference numeral M identifying the actual gunpowder charge which is located upstream of the damping material 2, that is inwardly of the same. This facilitates readying of the device for use because the charge and the damping means can now be introduced into the recess as a unit.

HQ. 5, finally, shows still another embodiment wherein the charge M- and wadding material-here identified with reference numeral 2."--are accommodated not directly in the recess but instead in a cartridge casing l" which is configurated to conform precisely to the cross-sectional configuration of the recess. The recess, and accordingly the cartridge casing l", will in FIG. 5 be seen to converge in cross section towards the outlet which communicates with the interior of the pressure chamber in which the pressure-transmitting liquid is accommodated. The embodiment of H6. 5 is thus in effect a modification of FIG. 2 in so far as operation is concerned, and a modification of FllG. d in so far as the structure is concerned, namely the accommodation of the wedding material 2'." in the cartridge casing.

The size of the space accommodating the wadding material-or left empty as in the case of the space of the portion in FlG. l-rnay be varied within a wide range, and similarly the volume of this space may be so varied. it has been found, however, that advantageous relationships will be obtained if the volume of the space accommodating the wadding material or, as in H6. i, being left free as identified with reference numeral 3, is approximately equal to that volume which is required for the charge. if the volume of the portion 3, which for the sake of simplicity is simply called the expansion chamber, is too large then the desired high working pressure can no longer be obtained. @n the other hand, if the volume is too small then the desired complete combustion of the guru powder charge is impossible to achieve.

The quantity of the charge, the configuration of the cartridge casing, the manner in which the charge is ignited, the type, geometry and size of the gunpowder grains as well as the size of the wadding material plug and the configuration of the expansion chamber are factors which contribute to defining the parameters both for the development of the working pressure and for the stresses which act upon the material sun rounding the recess when the charge is ignited. it is a particular advantage of the invention that it permits the chargewhether or not provided with a cartridge casing-to be configurated in a variety of different ways. This makes it possible to select from a plurality of possibilities which all provide the same advantageous operation that one which is most suitable and most advantageous from a point of view of economy and ease of handling. This is of great importance because the charge is a significant factor in the operating cost of explosiveforming devices.

it should still be emphasized that the embodiments illus trated in lFllGS. ll-5 may be combined with one another in various ways, that features of one embodiment may be combined with features of another embodiment, and that all such combinations of course are to be encompassed by the present invention.

it will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in an explosive-forming device, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

We claim:

l. An eirplosive-forming device, comprising wall means surrounding a pressure chamber arranged to accommodate a workpiece and a die having a surface contour which is to be imparted to said workpiece by shock deformation of the latter into conformance with said surface contour, said wall means including at least two wmls at least one of which is movable relative to the other between a chamber-closing position and a chamber-opening position, and said wall means having an inertia so selected as to at least substantially equal the necessary shock-pressure for producing the predetermined energy level requisite to obtain the desired deformation of said worlrpiece so that upon exceeding of said necessary shock-pressure relative movement of said walls to said chamber-opening position results with concomitant venting of said chamber; and shockpressure producing means for producing a sudden increase in pressure in said chamber, including a recess provided in said wall means and having an opening communicating with said pressure chamber, said recess including an inner portion of a smaller cross section and an outer expansion portion of a larger cross section intermediate and communicating with said inner portion and said chamber, a gunpowder charge and damping rneans accommodated in said inner portion of said recess intermediate said charge and said outer portion.

A device as defined in claim ll, wherein at said outer portion of said recess has a cross-sectional area which decreases in direction towards said opening.

3. A device as defined in claim l, wherein said outer portion of said recess converges conically in direction towards said opening.

ll. A device as defined in claim ll, wherein said inner portion is of constant cross-sectional configuration.

5. A device as defined in claim 4, wherein said recess is cylindrical.

b. A device as defined in claim ll, and further comprising a casing accommodating said gunpowder charge and said damping means, said casing being received in said recess and having an outlet directed towards and communicating with said opening.

'7. A device as defined in claim b, wherein said casing has an external configuration corresponding to the internal configuration of said recess.

h. A device as defined in claim '7', wherein said recess diverges conically in direction inwardly of said opening, and wherein said casing conically tapers interiorly and eiiteriorly in direction towards said outlet, said wedding means completely filling that part of the interior of said casing which corresponds to said remainder of said recess.

(llll 9. A device as defined in claim 1, said wadding means being ejected into said pressure chamber in response to combustion of said charge, and wherein said wadding means is composed of material which decomposes into small particles on entry into said pressure chamber so as to avoid damage in the latter.

10. A device as defined in claim 9, wherein said material is selected from the group comprising felt, paper board and nonvulcanized rubber. 

1. An explosive-forming device, comprising wall means surrounding a pressure chamber arranged to accommodate a workpiece and a die having a surface contour which is to be imparted to said workpiece by shock deformation of the latter into conformance with said surface contour, said wall means including at least two walls at least one of which is movable relative to the other between a chamber-closing position and a chamber-opening position, and said wall means having an inertia so selected as to at least substantially equal the necessary shock-pressure for producing the predetermined energy level requisite to obtain the desired deformation of said workpiece so that upon exceeding of said necessary shock-pressure relative movement of said walls to said chamber-opening position results with concomitant venting of said chamber; and shock-pressure producing means for producing a sudden increase in pressure in said chamber, including a recess provided in said wall means and having an opening communicating with said pressure chamber, said recess including an inner portion of a smaller cross section and an outer expansion portion of a larger cross section intermediate and communicating with said inner portion and said chamber, a gunpowder charge and damping means accommodated in said inner portion of said recess intermediate said charge and said outer portion.
 2. A device as defined in claim 1, wherein at said outer portion of said recess has a cross-sectional area which decreases in direction towards said opening.
 3. A device as defined in claim 1, wherein said outer portion of said recess converges conically in direction towards said opening.
 4. A device as defined in claim 1, wherein said inner portion is of constant cross-sectional configuration.
 5. A device as defined in claim 4, wherein said recess is cylindrical.
 6. A device as defined in claim 1, and further comprising a casing accommodating said gunpowder charge and said damping means, said casing being received in said recess and having an outlet directed towards and communicating with said opening.
 7. A device as defined in claim 6, wherein said casing has an external configuration corresponding to the internal configuration of said recess.
 8. A device as defined in claim 7, wherein said recess diverges conically in direction inwardly of said opening, and wherein said casing conically tapers interiorly and exteriorly in direction towards said outlet, said wadding means completely filling that part of the interior of said casing which corresponds to said remainder of said recess.
 9. A device as defined in claim 1, said wadding means being ejected into said pressure chamber in response to combustion of said charge, and wherein said wadding means is composed of material which decomposes into small particles on entry into said pressure chamber so as to avoid damage in the latter.
 10. A device as defined in claim 9, wherein said material is selected from the group comprising felt, paper board and nonvulcanized rubber. 